1. Field of the Invention
The present invention relates to an electric vehicle (EV) relay, and more particularly, to an electric vehicle relay capable of extinguishing an arc generated between a movable electrode and a fixed electrode by extending the arc in a mechanical manner.
2. Background of the Invention
Generally, a direct current (DC) relay or a electromagnetic contactor is a type of electric circuit switching apparatus for performing a mechanical driving and transmitting a current signal using a principle of an electromagnet. The DC relay or the electromagnetic contactor is installed at various types of industrial equipment, machines, vehicles, etc. Especially, a relay for an electric car may switch a conducted state of a main current by being positioned at a battery system.
FIG. 1 is a longitudinal section view of an electric vehicle (EV) relay in accordance with the conventional art. FIG. 2 is a horizontal section view illustrating a magnetic field of a contact part of an EV relay in accordance with the conventional art. FIG. 3 is a partial perspective view illustrating a contact part of an EV relay in accordance with the conventional art.
A direct current (DC) relay for an electric car includes an outer case 1, a arc chamber 2 installed in the outer case 1, a pair of fixed contacts 3 fixedly-installed at the arc chamber 2, and a movable contact 4 movable to contact or be separated from the fixed contacts 3. The DC relay generally includes an electric actuator for driving the movable contact 4 so that switching of contacts can be controlled by an external power. The actuator includes a driving shaft 5 coupled to the movable contact 4, a fixed core 6, a movable core 7, a coil 8, etc. A permanent magnet 9 is provided in the arc chamber 2 so as to effectively control an arc generated between the fixed contact 3 and the movable contact 4 during a current interruption operation.
The fixed contacts 3 are configured as a main contact terminals having polarities of (+) and (−). A magnetic field generated from the permanent magnet 9 performs an interaction with a current, thereby generating a force by Fleming's left-hand law. Thus, the magnetic field pushes out an arc generated during a switching operation, so that damage of a contact part can be reduced.
FIG. 2 illustrates a polarity of a contact and an operation of a force by the permanent magnet 9. A magnetic field (B) toward an S-pole from an N-pole is applied to the permanent magnet 9. An electric force (+I) is generated from the right fixed contact 3, in a exiting direction perpendicular to the drawings. An electric force (−I) is generated from the left fixed contact 3, in a entering direction perpendicular to the drawings. Thus, an arc receives forces (F, F′) in an outer direction right and left according to Fleming's left-hand law, so that damage applied to the contact part can be prevented.
In the conventional EV relay, a magnetic field generated by the permanent magnet 9 extinguishes an arc generated between the fixed contacts 3 and the movable contact 4, in an extending manner.
However, the conventional EV relay has the following problems.
Firstly, since a permanent magnet should be provided, production costs are increased.
Secondly, a magnetic field generated from the permanent magnet 9 increases an electronic repulsive force by Fleming's left-hand law, together with a direction of a current flowing on the movable contact 4 as the fixed contacts 3 and the movable contact 4 come in contact with each other.
This will be explained in more detail with reference to FIG. 3. A current (I) flows from a left movable contact 4a to a right movable contact 4b. Thus, a force (F1) is applied to the movable contact 4 in a downward direction, i.e., a direction to separate the movable contact 4 from the fixed contacts 3 according to Fleming's left-hand law. Due to such an electronic repulsive force, an inferior contact state occurs.